1. Field of Invention
The present invention relates to an active-matrix electro-optical device, a method for driving the active-matrix electro-optical device, a scanning line driving circuit, and electronic equipment.
2. Description of Related Art
Active-matrix electro-optical devices typically include a plurality of scanning lines and a plurality of data lines, respectively extending horizontally and vertically, and a switching element, such as a thin-film diode (hereinafter referred to as xe2x80x9cTFDxe2x80x9d) or a thin-film transistor (hereinafter referred to as xe2x80x9cTFTxe2x80x9d) arranged at each of intersections of the scanning lines and the data lines.
The scanning lines are successively provided with a scanning signal by a scanning line driving circuit. The data lines are driven by a data line driving circuit. In synchronization with a successive supply of the scanning signal, the data line driving circuit feeds a sampling control signal to a sampling switch that samples, on a data-line-by-data-line basis, a video signal supplied to a video signal line.
In such an active-matrix electro-optical device, a vertical scanning operation on a field-by-field basis or on a frame-by-frame basis, i.e., a field scanning or a frame scanning, is performed in response to the scanning signal and the sampling control signal.
The video signal input to the electro-optical device may be a signal of any of the digital TV system and the like other than the NTSC system, the PAL system, SECAM system, and high-vision system. The number of video lines of the video signal is different from television system to television system. The electro-optical device compatible with a plurality of television systems thus includes a video line count converter. Using the video line count converter, the number of lines of the input video signal is converted to correspond with the number of scanning lines of the active matrix, and the converted video signal is used to drive the scanning line driving circuit and the data line driving circuit.
The video line count converter typically employs a field memory or a frame memory for converting the video line count, and generally increases the scale of the circuit of the entire electro-optical device. Particularly, a device, such as a video projector, in need of three processing circuits corresponding to the three RGB colors, disadvantageously requires the tripled circuit scale of the video line converter to perform process for the three colors.
The present invention has been developed at least in view of this problem, and it is an object of the present invention to at least provide an electro-optical device which converts the video line count without using a video line count converter, a method for driving the electro-optical device, a scanning line driving circuit, and electronic equipment.
One exemplary embodiment of the present invention lies in a method for driving an electro-optical device that includes a pixel including a switching element arranged at each of intersections of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element, a scanning signal for driving each of the plurality of the scanning lines being preferably generated in accordance with the video line count per field of an input video signal and a scanning line count.
In accordance with this exemplary embodiment of the present invention, the scanning signals are generated in accordance with the video line count per field of the input video signal and the scanning line count. A decimation process is thus performed by deactivating the scanning signal for particular video lines of the video signal or a stretching process is performed by concurrently activating the scanning signal supplied to adjacent scanning lines for the particular video lines. With this arrangement, even if the video line count of the input video signal fails to coincide with the scanning line count, the input video signal is presented on the electro-optical device without the need for the converter for converting the video line count.
In the generation step of the scanning signal in the driving method, all scanning signals may be deactivated for the particular video lines predetermined in accordance with the detected video line count and the scanning line count. Since the scanning signals for the particular video lines are deactivated, the video signal of the particular video lines is not written on pixels. The particular video lines are thus decimated.
The driving of the data line is preferably suspended for the particular video line while the data lines are driven on the video lines other than the particular video lines. Since the video signal is not written on the particular video line, the data line does not need driving. The suspension of the driving of the data line for the particular video line creates no problem, and provides the advantage of reducing power consumption.
In the generation step of the scanning signal in the driving method, two scanning signals for driving adjacent scanning lines are preferably concurrently activated for the particular video lines predetermined in accordance with the detected video line count and scanning line count. Since the two scanning signals for driving the adjacent scanning lines for the particular video lines are concurrently activated, the switching elements connected to the adjacent scanning lines are concurrently turned on, and the video signal is written on the video lines corresponding to the two scanning lines. The arrangement achieves the stretching process.
Another exemplary embodiment of the present invention lies in a method for driving an electro-optical device that includes a pixel including a switching element arranged at each of intersections of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element, the video line count per field of the input video signal being detected, the scanning signals for driving the scanning lines being successively generated when the detected video line count is equal to the scanning line count, and the scanning signals for the particular video lines predetermined in accordance with the detected video line count and the scanning line count being deactivated when the detected video line count exceeds the scanning line count, while two scanning signals for driving adjacent scanning lines being concurrently activated for the video lines other than the particular video lines.
In accordance with this exemplary embodiment of the present invention, the video signal for the particular video lines is decimated while the other lines are twice stretched. When the video signal, having the video line count equal to the scanning line count, is input, the video signal is presented without the need for the decimation process or the stretching process. When both line counts fail to coincide with each other, the decimation process or the stretching process is performed by controlling the scanning signal. For instance, when a video signal having 540 lines per field is input against a scanning line count of 720, the decimation process is carried out to decimate one line every three lines, while the stretching process for stretching the lines is performed.
Another exemplary embodiment of the present invention lies in a method for driving an electro-optical device that includes a pixel including a switching element arranged at each of intersections of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element, the video line count per field of the input video signal being detected, the scanning signals for driving the scanning lines being successively generated when the detected video line count is equal to the scanning line count, and two scanning signals for driving adjacent scanning lines for the particular video lines predetermined in accordance with the detected video line count and the scanning line count being concurrently activated when the detected video line count exceeds the scanning line count.
Since the video signal of the particular video lines is written on the pixels connected to the two scanning lines in accordance with this exemplary embodiment of the present invention, the particular video lines are twice stretched. When the video signal, having the video line count equal to the scanning line count, is input, the video signal is presented without the need for the decimation process or the stretching process. When both line counts fail to coincide with each other, the decimation process or the stretching process is performed by controlling the scanning signal. For instance, when a video signal having 540 lines per field is input against a scanning line count of 720, the stretching process is carried out on one line every three lines for image presentation.
Another exemplary embodiment of the present invention lies in a scanning line driving circuit of an electro-optical device includes a pixel including a switching element arranged at each of intersections of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element. The scanning line driving circuit includes a shift device which successively outputs a transfer signal by transferring a start pulse in response to a clock signal, and an output selection device which generates a scanning signal for driving a respective scanning line by selecting a predetermined duration within an active period of the transfer signal, based on an enable signal that is generated in accordance with the video line count of the input video signal and the scanning signal line count.
In accordance with this exemplary embodiment of the present invention, provided with the enable signal, the output selection device generates the scanning signal for driving the respective scanning line by selecting the predetermined duration within the active period of the transfer signal generated by the shift device. The scanning signal is thus flexibly controlled by the enable signal. Since the enable signal is generated in accordance with the video line count of the input video signal and the scanning line count, the decimation process or the stretching process is performed by controlling the scanning signal even if the video line count of the input video signal and the scanning line count fail to coincide with each other.
The output selection device includes a plurality of unit circuits corresponding to the respective transfer signals, and the unit circuit includes a plurality of branch lines to which the transfer signal is distributed, and a logic circuit, arranged for each branch line, for generating a signal that is activated only when the transfer signal distributed along the branch line and the enable signal are concurrently activated, and for outputting the signal as the scanning signal.
An electro-optical device of another exemplary embodiment of the present invention includes the scanning line driving circuit, a detecting device for detecting the video line count per field of the input video signal, and a signal generator for generating an enable signal which is responsive to the detected video line count and the scanning line count, and which is deactivated for predetermined durations of time prior to and subsequent to the timing of line switching.
Since the enable signal is deactivated for predetermined durations of time prior to and subsequent to the timing of line switching with this arrangement, the scanning signal is also deactivated throughout these durations. As a result, this arrangement reliably prevents the scanning signals from overlapping each other in the active periods thereof, thereby improving image quality.
An electro-optical device of another exemplary embodiment of the present invention includes a scanning line driving circuit, a detecting device for detecting the video line count per field of the input video signal, and a signal generator for generating an enable signal which is deactivated for particular video lines predetermined in accordance with the detected video line count and the scanning line count.
In accordance with this exemplary embodiment of the present invention, the scanning signals are generated in accordance with the video line count per field of the input video signal and the scanning line count. A decimation process is thus performed by deactivating the scanning signal for the particular video lines of the video signal or a stretching process is performed by concurrently activating the scanning signal supplied to adjacent scanning lines for the particular video lines. With this arrangement, even if the video line count of the input video signal fails to coincide with the scanning line count, the input video signal is presented on the electro-optical device without the need for the converter for converting the video line count.
The electro-optical device preferably includes a data line driving circuit for driving the data line in accordance with the shift signal that is generated by successively transferring a start pulse in response to a clock signal, wherein the signal generator supplies the data line driving circuit with the start pulse for the video lines other than the particular video lines while stopping the supplying of the start pulse to the data line driving circuit for the particular video lines.
With this arrangement, the start pulse is not supplied to the data line driving circuit in connection with the particular video lines not contributed to image presentation, and the data line driving circuit suspends the transfer operation thereof. The power consumption of the data line driving circuit is thus reduced.
An electro-optical device of another exemplary embodiment of the present invention includes the scanning line driving circuit, a detecting device for detecting the video line count per field of the input video signal, and a signal generator for generating an enable signal which concurrently activates two scanning signals for driving adjacent scanning lines for the particular video lines predetermined in accordance with the detected video line count and the scanning line count. With this arrangement, the stretching process is performed by controlling the scanning signal in accordance with the video line count of the input video signal.
An electro-optical device of another exemplary embodiment of the present invention for alternating the polarity of a video signal to be written to pixels according to the unit of at least one scanning line, includes a polarity control device for controlling the electrode of the video signal on a line-by-line basis for the particular video lines so that the number of scanning lines supplied with a positive video signal is equal to the number of scanning lines supplied with a negative video signal.
With this arrangement, the polarity inversion of the video signal is performed in consideration of the particular video lines to be subjected to the decimation process or the stretching process. For instance, the stretching process is performed on one line out of the three lines, the video signal of the positive polarity is fed to two consecutive lines, and then the video signal of the negative polarity is fed to two consecutive lines.
An electro-optical device of another exemplary embodiment of the present invention inputting an input composite video signal and presenting an image on a display area, includes a video line count detector circuit for detecting the video line count of the input video signal per field or per frame, and a signal processing circuit for comparing a signal detected by the video line count detector circuit with a line count of the display area of the electro-optical device, and for processing a particular video line of the input composite video signal in accordance with the line count of the display area to convert the composite video signal into a component video signal.
The signal processing circuit of the electro-optical device converts the input composite video signal, having a video line count smaller than the line count of the display area, into a component video signal in a manner such that the particular video line of the input video signal is presented on a plurality of lines of the display area.
The signal processing circuit of the electro-optical device converts the input composite video signal, having a video line count greater than the line count of the display area, into a component video signal in a manner such that the particular video line of the input video signal is not presented on the lines of the display area.
An electro-optical device of another exemplary embodiment of the present invention receiving an input composite video signal and presenting an image on a display area, includes a determining circuit for determining the type of the input composite video signal, and a signal processing circuit for generating a component video signal in accordance with the line count of the display area, based on the determination result provided by the determining circuit and the line count of the display area of the electro-optical device.
Electronic equipment of various exemplary embodiments of the present invention includes the above-discussed electro-optical devices. For instance, the electronic equipment may be a video projector, a liquid-crystal television, a viewfinder type or direct monitoring type video cassette recorder, a car navigation system, a pager, a word processor, a workstation, a video telephone, etc.